Method and means for selectively controlling metal-pickling baths



252. COMPOSITIONS,

Patented Nov. 19, 1929 UNITED STATES hxamjner IAKES E. GBAVELL, OF ELKINS PARK, PENNSYLVANIA, ASSIGNOB TO AMERICAN CHEMICAL PAINT COMPANY, OF AIBLEB, PENNSYLVANIA, A CORPORATION 01 DELAWARE IETEO]? AND BEAN S FOB SELECTIVELY CONTROLLING KETAL-PICKLHVG BATES Io Drawing. Application med July 16,

This invention relates broadly to the art of pickling and specifically to selectively controlling the action of pickling baths.

The objects of this invention are to save 5 metal, acid and time; to reduce acid brittleness and obnoxious fumes, to lower the costs of selective controlling agents, and to generall improve the art of pickling.

l t has been discovered that thioamides act as powerful agents for selectively controlling metal pickling baths in that they reduce the action of the bath on the metal to be cleaned of its scale without hindering the action of the bath in removing the said scale. Of these 1 thiourea has been especially proposed. They ave, owever, not attained extended commercial use, principally because of their high cost in relation to competing materials.

I have discovered that the quantity of a thioamide required for selectivity controlling Water 3300.00 gallons Sulphuric acid (66) 100.00 gallons Thiourea 1.58 pounds Gelatine .40 pounds This bath may be used cold but in order that it act rapidly on the immersed material it may be heated to any degree up to the boiling point of water. When used heated to 180 F. it will remove the scale from steel in about fifteen minutes, more or less, this being the same time that is required for an uncond1 trolled bath, yet the bath may be used approximately twice as long, and consequently pickle twice the quantity of steel as an uncontrolled bath, before suflicient metal has been dissolved in the bath to render it unfit for further use.

1927. Serial No. 206,387.

Had either of the control ingredients been used alone, in the proportions indicated, the bath would have lasted only approximately one and a quarter times as long as if uncontrolled. To make the bath last twice as long with gelatine alone, and without rolonging the time of pickling and thus de eating the object of the pickling bath, would have been impossible; to make the bath last twice as long by the addition of thiourea alone would have required approximately 4 pounds of thiourea instead of the 1.58 pounds as indicated by my formula.

For convenience the W atine ay be compounded in a vance an e admixture added to a regular pickling bath after the bath has been made up, using them in the proportion given in my formula. If desired water may be added to the dry admixture so as to form a liquid control, in which case the following proportions may be used:

Thiourea 1.58 pounds Gelatine .40 pounds Water .86 pounds The gelatine should be melted in about half the water and the thiourea dissolved in the remainder and the two solutions then mixed together. A few drops of sulphuric acid (66) may be added in case the admixture does not remain liquid.

It is my understanding that the nascent hydrogen liberated by the action of the acid solution on the metal acts on the thiourea to form formaldehyde which in some unknown manner selectively controls the action of the bath on the metal and that the gelatine acts to reinforce this action and hence any equivalent substance in so far as it produces this result may be substituted for the gelatine without departing from the spirit of this invention.

A soluble colloid such as gel [OCCU a a claim:

1. The method of reinforcing the selective control effects of thioamides in a pickling bath which comprises causing a thioamide in the pickling bat to exert its selective control efiect in the presence of a dispersing subatine acts as a stance that will reinforce the selective control efiect of the said thioamide.

2. The method of reinforcing the selective control efiect of a thioamide in a pickling 5 bath which comprises causing the thioamide to exert its effect in the presence of a dispersing and reinforcin agent.

3. The method of reinforcing the selective control efl'ect of a thioamide in a pickling 1 bath which comprises causing the thioamide to exert its effect in the presence of gelatine.

4. The method of reinforcing the selective control effect of thiourea in a pickling bath which comprises causing the thiourea to exert its effect in the presence of gelatine.

5. In the art of pickling metals in a bath of metal etching acid and thioamides the improved process which consists in augmenting the selective control of the acid and eilecting a saving in the quantity of thioamide used by replacing a modicum of the thioamide with a colloid substance soluble in the bath.

6. A pickling bath comprising a thioamide and a dispersing agent to reinforce the selective controlling effect of said thioamide.

7. A pickling bath comprising water, sulphuric acid, a thioamide and gelatine.

8. A pickling bath comprising water, sulphuric acid, thiourea and gelatine.

9. A dry material for selectively controlling the action of pickling baths comprising an admixture of a thioamide and a dispersing material for reinforcing the selective control effect of said thioamide substantially in the proportion of 1.58 pounds of thioamide to .40 pounds of dispersing material.

10. A dry material for selectively controlling the action of a pickling bath comprising an admixture of a thioamide and gelatine substantially in the proportion of 1.58 pounds of the former to .40 pounds of the latter.

11. A dry material for electively controlling the action of a pickling bath comprising an admixture of thiourea and gelatine substantially in the proportion of 1.58 pounds of the former to .40 pounds of the latter.

12. A material for selectively controlling the action of a pickling bath comprising an admixture of a thioamide, gelatine and water substantially in the proportion of thioamide 1.58 pounds, gelatine .40 pounds and water .86 pounds.

13. A material for selectively controlling the action of a pickling bath comprising an admixture of thiourea, gelatine, water, and sulphuric acid substantially in the proportion of thiourea 1.58 pounds, gelatine .40 pounds, water .86 pounds, and sulphuric acid a few drops.

JAMES H. GRAVELL. 

